How to programmatically determine the installed version of IE from a script

We have an automated testing cluster based on selenium-grid.

To manage the cluster, I have built a collection of Rake (Ruby) tasks which can start, restart, ping, and stop nodes. I'm testing our application across a number of browsers including IE6, IE7, and IE8. This means each node in the cluster has to be aware of which version of IE is installed so that it can claim the correct selenium-grid profile name (eg:

"IE6 on Windows XP"

vs.

"IE8 on Windows Vista"

), so that certain tests can be written against those browsers.

My question:

I'd like to cut down on the configuration work here. How do I programmatically determine which version of IE is running on the current system? I have tried the following technique:

wmic product where "Vendor like '%Microsoft%'" get Name, Version

But this only returns versions of programs that were installed with the Windows Installer, so IE doesn't show up in this list.

Ideally I'd like to be able to determine this from inside of a Rake script, or at least something that's callable from a Rake script.